Prior to setting forth a short discussion of the related art, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “Wi-Fi” as used herein may include any wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards”.
The term “Access Point” or “AP” as used herein is defined as a device that allows wireless devices (known as User Equipment or “UE”) to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself.
The term “User Equipment” or “UE” as used herein is defined as any device that has wireless communication capabilities, specifically, the IEEE 802.11 standards. A UE may be for example a smart telephone, a laptop, a tablet or a personal computer (PC).
The term “Station” as used herein is defined in compliance with the IEEE 802.11 standards as any node on the wireless network. Thus, both UEs and APs are considered in this context to be “Stations”.
The terms “Distributed Coordination Function” (DCF), “Distributed Interframe Space” (DIFS), and “Short Interframe Space” (SIFS) as used herein are types of InterFrame Spacings as defined in the IEEE 802.11 standards.
The term “MultiBeam Access Point” (MBAP) as used herein is an AP that includes multiple AP operating simultaneously on the same radio channel where directive beams and other technology enable collation of AP.
The term “beamformer” as used herein refers to analog and/or digital circuitry that implements beamforming and includes combiners and phase shifters or delays and in some cases amplifiers and/or attenuators to adjust the weights of signals to or from each antenna in an antenna array. Digital beamformers may be implemented in digital circuitry such as a digital signal processor (DSP), field-programmable gate array (FPGA), microprocessor or the CPU of a computer to set the weights as may be expressed by phases and amplitudes of the above signals. Various techniques are used to implement beamforming, including: Butler matrices, Blass Matrices, and Rotman Lenses. In general, most approaches attempt to provide simultaneous coverage within a sector using multiple beams.
The term “Clear Channel Assessment” (CCA) as used herein refers to the CCA function as defined in the IEEE 802.11 specifications.
The term “Energy Detection” (ED) as used herein refers to the part of the CCA function as defined in the IEEE 802.11 specifications.
The term “Preamble Detection” as used herein refers to the part of the CCA function that detects the preamble as defined in the IEEE 802.11 specifications.
The term “Back Off” (BO) procedure as used herein refers to the Back Off process as defined in the 802.11 specifications.
The term “Base Band Processor” (BBP) as used herein refers to encoding data and decoding data so as to create the required WiFi baseband signal for all versions of the 802.11 protocol(s).
WiFi has been implemented with a limited amount of frequency resources that use collision avoidance techniques to allow multiple user equipment's (UEs) to share the same channel. As the numbers of UEs proliferate, the impact of such a scheme restricts the ability of collocated Wi-Fi access point (AP) to support an ever increasing number of users. Unsynchronized operation between APs means a transmitting AP's signal may interfere with the reception of another AP that uses the same channel unless sufficient isolation (e.g., exceeding 125 dB) is provided between the transmitting and receiving functions.
Some known solutions address the aforementioned problem by using physically separated antenna arrays for transmit and receive and by providing cancellation of each transmitted signal within the receiver processing functions, achieving about 100 dB of isolation, short of what is required.